In certain welding operations, it is necessary that the welding tip of the welding apparatus or welding tool be accurately moved along the line of the weld in order that a uniform weld may be achieved. Accuracy of travel of the welding tip is especially necessary in the case of girth welds employed to weld pipes together end-to-end. Similar considerations are important in doing other types of work on pipes or other objects. Pipelines of relatively large size designed to carry petroleum products therethrough must be welded together end-to-end by strong dependable welds because of the dangers inherent in the products which they carry. Uniformity of the welds is necessary in order that they will have adequate strength and dependability to prevent cracking and ruptures at the welds, and in addition, uniformity of the welds is necessary in order that penetrations of the welds at the pipe interiors will be controlled so as not to provide a hindrance to fluid flow through the pipelines. Similar requirements may also pertain to other equipment, such as tanks and processing equipment, especially those in which hazadous material is contained.
Where welding is done by hand, the welder may retrace his path to cure deficiencies in the welds as the welding proceeds. In the case of automatic welding, however, the welding must be done in continuous non-stop fashion and no retracing of the weld path or pass may be done. Therefore, in the case of automatic welding, it is extremely important that the welding tip accurately and uniformly follow the line of the weld in order that adequate strength and dependability of the weld may be obtained.
Welding or working carriages known in the art are shown in U.S. Pat. Nos. 3,229,883, 3,753,525, and 3,844,468. The carriages shown in these patents do not provide adequate stability of the welding apparatus travel to meet the requirements of automatic welding of pipelines for high pressure service, or for doing other comparable work upon a pipeline or other workpiece.
The instant invention seeks to provide a carriage for welding or other purposes of novel improved design.